Many residential homeowners rely on the use of a well to supply water to their home. Likewise, many farmers rely on the use of a well to supply water to irrigate crops or to keep animals hydrated. Private water wells are a common feature in areas where municipal or city water services are unavailable or where surface supplies are not sufficient or accessible. Water wells are commonly used to source groundwater where naturally occurring groundwater exists in spaces between rocks and/or sand. The wells themselves are bore holes either drilled or pressed into or through the ground into which casing pipes, screens, pumps and other water plumbing are installed. Groundwater seeps through openings in the casing pipe called screens. Water can be pumped via these wells, either with an above ground vacuum pump or, where the water is deeper than 30 feet, with a submersed pump that creates upward pressure to move the water to the surface.
A conventional well typically includes a borehole from the surface to a required depth to reach the ground water. A casing pipe is inserted into the borehole and grout is used to seal the space between the casing pipe and the earth. A pump (either submersed or above the ground water surface, depending on depth) is attached to the water pipe for transportation of water from the well to the point of use. The well is capped at the well head on the ground surface with a well cap. Typically, information which may include a service contractor's phone number and a date of service may be recorded on the well cap.
Water well construction (and sometimes site selection or location advisement) is done by a well driller, who takes care to design the well to meet the needs of the people who will use the water. The well driller, in the process of planning and drilling, will determine where there is ample groundwater, and will size the length and diameter of the well and casing pipe and the capacity and location of the pump accordingly. The driller will take special care to know the top elevation and the productivity of the groundwater table. Elevation is often found by measuring down from the well head (top of the well) to the water surface. Productivity of the well is inferred by measuring the elevation of the water and time it takes to return to a resting level after a pumping event has removed water to the well, a process called recovery. Together with elevation and productivity, the final pump selection is made and construction can be completed.
This water information is necessary to determine the well location in relation to the location of a building, a field of crops, or a neighborhood. At also informs the semi-permanent placement of the pump in the well. If the pump is placed too high in the well, it risks running dry and breaking prematurely. If the pump is placed too low in the well, then the owner will pay extra for the energy required to pump water an unnecessary distance. This information is typically only gathered once, however, at the time of construction. The lack of subsequent information gathering sometimes leads to new issues with the well or the pump that could have been prevented if only the well driller or homeowner had such information.
A borehole well may be considered to be healthy as long as sufficient ground water seeps through a screen section of the casing pipe into the column to allow for water to be pumped from the well. This state of balanced supply and demand is called a “safe yield”. As is known to those skilled in the art, a borehole well, the water system, and sometimes the pump equipment will not tolerate long periods of an unsafe yield. For example, a submersible pump must be kept submerged under water for proper operation. Failure to keep the pump submerged causes the pump to overheat and fail. Failure of a pump requires the well to be opened by a technician and the pump must be physically retrieved and repaired or replaced. Thus, a previously recognized problem has been that it is difficult to know the water level in the well and how close the pump may be to reaching the unsafe yield point. In a worst-case example, a borehole well will be pumped dry, the pump will fail, and the water table will have been permanently lowered in the area, effectively rendering the well useless. Needless to say, it is desirable to know about water levels in the casing pipe.
Existing methods of determining water table levels include mounting a sensor under the water in the well with wires communicating to the well head, pressure sensors built into the pump, and opening the well head to physically inspect the well with a plumb bob. Various other methods are known which all necessitate physically opening the well head to inspect the water table level.
One unsatisfactory previously recognized approach, in an attempt to solve the problem referred to herein, involves use of an airline to compress air in the casing pipe in an attempt to raise water to the surface, indicating the level. Another unsatisfactory method is to use a simple sonar instrument, not unlike a consumer grade fish finder, to find water level in the well. Certain environmental factors, like temperature, casing pipe material, well straightness, depth, and obstructions can render these devices inaccurate, so they are not as popular as mechanical tapes. In yet another previously recognized approach, contractors often carry a well level device that includes a moisture sensor at the end of a measuring tape that is temporarily inserted into a well and which makes a sound when it touches water, indicating the distance to the water. This technique is known to be reliable and inexpensive, but like the other previously described techniques, it is only designed for the well contractor's use to take one reading at a time, and to not log data or spot trends without repeat visits and manual collection, which is impractical and rarely happens.
A disadvantage of these previously recognized approaches is that due to water levels in the ground being dynamic, the data acquired is quickly dated and inaccurate once the technician completes the test. There is virtually no ongoing monitoring of safe yields of the well's water level. Additionally, users do not know if they are using more water than they should until it is too late. One common indication of overuse is that the pump fails due to dry run, indicated by a lack of running water from faucets or to toilets or appliances. Failures caused by overuse can be very expensive to repair, ranging in price from thousands of dollars to replace a pump or clear a well, to tens of thousands of dollars to dig a deeper well. In some cases, systemic overuse by many consumers in a region can even tax the ground water to the point of concentrating pollution or even running everyone's well dry. Homes in areas where there is severe water risk can quickly lose value.
On higher capacity, higher criticality water wells owned by water municipalities and some high-use agriculture businesses, water elevation information is collected continuously with pressure sensors mounted in the well under the water level connected to data logging equipment at the surface. Data provided by these devices is vital for controlling flow and therefore system performance. So a pressure sensor is part of a larger SCADA (Supervisory Control and Data Acquisition) system that keeps water flowing continuously. But these devices are expensive to install and maintain and may be part of a larger control network and scheme so they are not suitable or economically viable for homeowner or intermittent farm or business use.
When commissioning or repairing a well, a well driller may also perform a “pump test” to determine the ideal location for the pump. Using a sacrificial test pump, the well driller tests the pumping level and drawdown of the well, that is, the changed water elevation while the pump is running at its target capacity. The process involves installing the sacrificial test pump in the well deep under the static water level and running it at a flow rate equal to the anticipated peak demand of the well. When water is pumped to the surface, the water level in the well drops dramatically at first, and then the rate of decline begins to decrease until the pressure created by the water table equals the pressure created by the pump and groundwater runs into the well at the same rate that the well pumps water to the surface. The level of the water at which the pressure created by the water table equals the pressure created by the pump is the ideal vertical position of a pump in the column. Of course, the ideal vertical position of the pump at the time of commission or repairing may not be the ideal vertical position in a day, a month, or even years after the pump test is performed. However, because performing pump tests as described are costly and time intensive, they are not performed until repair is needed.
Finally, whereas in the recent past, sparse rural population, stable weather and slower agricultural and economic development did not threaten the natural recharge capabilities of most groundwater sources, today, population, overconsumption and climate changes have begun to tax the groundwater resource measurably. Hydro-geologists call this “unsafe yield.” So water wells constructed a few years ago based on a groundwater elevation measured at the time are not able to produce as designed, and often fail prematurely.
As discussed, monitoring groundwater elevation continuously in residential and agricultural wells is becoming more important, but existing monitoring solutions are not effective. Measuring with a tape continuously is impractical and will always only be for one time use (a snapshot taken at one moment). Measuring with inaccurate sensors does not yield usable information. Outfitting intermittent use wells with pressure sensors and control networks is not cost effective or even necessary. Smart operations methods and an understanding of trends are needed as conditions change.
What is needed therefore is a device that allows monitoring of the well's water level on a continual basis. What is also needed is a way to monitor the well's water level preferably without repeated removal of the well head. Further, what is needed is a way to retrofit existing wells with a device that continuously monitors the well's water level preferably without repeated removal of the well head. Heretofore, these requirements have not been fully met without incurring various disadvantages.